Your result
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Enter your values, then click Calculate result.How this calculator helps
Estimate room air-conditioner BTU capacity from an official area table, or calculate heating output from your own design load per square foot. The cooling mode is a room air-conditioner estimate based on ENERGY STAR’s floor-area reference for an eight-foot ceiling. It is not a whole-house cooling-load calculation. Windows, insulation, leakage, humidity and local climate can change actual requirements. The implemented table applies from 100 to under 2,500 square feet, and the calculator rejects area outside that scope instead of extrapolating a capacity. Confirm unusual room conditions with an installer.
How to use it
- 1
Choose the stated method or shape and read the labels before replacing the example values.
- 2
Enter the measurements in the exact units shown. Use the inputs described in the methodology below.
- 3
Click Calculate result. Editing inputs keeps the previous submitted result visible until you calculate again.
- 4
Compare the supporting figures with the formula and worked example, then review the method’s specific limitations.
Formula and methodology
Cooling uses the ENERGY STAR floor-area capacity table with ±10% shade/sun adjustment, +600 BTU/h per person above two and +4,000 BTU/h for a kitchen. Heating estimate = area × entered load. One cooling ton = 12,000 BTU/h.
The calculator applies the displayed arithmetic to the values entered on this device. It does not silently load a local tax rate, currency conversion or commercial assumption.
Worked calculation example
A 200 ft² ordinary room with two occupants maps to 6,000 BTU/h. Very sunny exposure raises that estimate to 6,600 BTU/h.
How to interpret your result
This method applies only within the stated scope. Room table estimate for an 8-ft ceiling, not a Manual J design. Heating load is entirely user supplied. Does not select equipment or estimate electricity use. The worked scenarios below identify the measurements and conventions needed to interpret the displayed output.
For different inputs or formulas, use Square Footage Calculator; Roof Area Calculator; Unit Price Comparison Calculator.
Related questions this calculator covers
- btu calculator
- air conditioner size calculator
- heating btu calculator
- furnace size calculator
Scenario comparison
| Scenario | What it shows |
|---|---|
| 200 ft², normal exposure, two occupants | 6,000 BTU/h reference estimate. |
| Same room, very sunny, three occupants, kitchen | 11,200 BTU/h after stated adjustments. |
| 200 ft² with entered heating load 30 BTU/h per ft² | 6,000 BTU/h supplied-load estimate. |
Common mistakes to avoid
- Using a room AC table as a whole-house HVAC design.
- Confusing cooling capacity with electric power consumption.
- Using a heating factor without a defensible heat-loss assessment.
Reproduce the equation shown on this page using the same entered values. A 200 ft² ordinary room with two occupants maps to 6,000 BTU/h. Very sunny exposure raises that estimate to 6,600 BTU/h. Keep input units and the selected method with any recorded result. Check unusual measurements rather than relying on extra displayed decimal places.
Authoritative reference. Room table estimate for an 8-ft ceiling, not a Manual J design. Heating load is entirely user supplied. Does not select equipment or estimate electricity use.What can affect the result?
Area and capacity brackets
Measure the floor in feet and multiply length by width. Divide an irregular room into simpler shapes and add the areas before entering the result. The table assigns capacity in brackets rather than applying one constant BTU figure to every square foot. At a boundary, this implementation selects the next listed bracket. That convention is disclosed because the table’s adjacent wording can look ambiguous. Use a measured floor area and avoid rounding downward to obtain a smaller recommendation.
Sun, people and kitchens
Select heavily shaded, normal or very sunny exposure. The sun adjustment changes the base table capacity before extra occupants or the kitchen amount are added. Only occupants above two receive the extra-person adjustment. Kitchen mode adds the specified room-cooling allowance; it does not model individual appliances or commercial cooking exhaust. The tonnage output is a unit conversion of estimated cooling capacity, not proof that a particular product size or efficiency is suitable.
Heating requires a supplied load
Heating mode has no automatic climate factor. You must enter a heat-loss load in BTU per hour per square foot from a suitable design or professional assessment. Multiplying by area estimates required delivered heat under that assumption. A furnace’s fuel-input rating differs from delivered output and depends on efficiency. The tool does not select a furnace, handle duct losses, size electrical equipment or replace an HVAC load calculation.
Privacy and browser processing
Values entered on this page are processed in the current browser session. SolvePilot does not require an account and does not receive the values entered into the calculator. Refreshing or closing the page clears the working values unless the browser itself restores a previous session. Avoid entering identifying or account information because the calculation needs summary values only.
Accuracy and verification
Accuracy depends first on input quality. Confirm definitions, scales, dates and source information before entering a value. Keep an independent record of any result used for planning because this page does not create an official statement or retain a calculation history.
Limits of this estimate
Room table estimate for an 8-ft ceiling, not a Manual J design. Heating load is entirely user supplied. Does not select equipment or estimate electricity use.
Sources and review information
Frequently asked questions
What size air conditioner do I need?＋
Room mode provides a starting capacity estimate for the entered floor area, exposure, occupancy and room type within the table’s scope. For high ceilings, unusual windows, multiple rooms or a whole house, obtain a proper load calculation rather than treating this estimate as a final equipment choice.
How many BTU are in one AC ton?＋
One cooling ton equals 12,000 BTU per hour. Divide the calculated hourly cooling capacity by 12,000 to obtain the equivalent tonnage. This is a capacity unit; it is not the electrical consumption or physical weight of the air conditioner.
Can I use this as a furnace size calculator?＋
Only if you supply an appropriate design heating load. The output is area multiplied by that supplied load, labeled as an entered-load estimate. It does not infer insulation, outdoor design temperature or furnace efficiency and should not be treated as automatic furnace selection.
Why reject small or very large rooms?＋
The implemented official cooling table begins at 100 ft² and ends below 2,500 ft². Extrapolating beyond the reference would add an unsupported method. The calculator therefore asks for professional assessment rather than fabricating a capacity from an unrelated constant.
Why can oversized AC be a problem?＋
A unit can cool air before adequately removing humidity. Capacity should match the room and installation conditions. The estimate is one input to selection; review manufacturer specifications and get advice for unusual loads or building conditions.